Secondary lightning arrester with arc spinning means



Oct. 27, 1964 E. H. YoNKERs ETAL 3,154,718

SECONDARY LIGHTNING ARRESTER wrm ARG SPINNING MEANS Filed March 16, 1962'4 HG2 I6 '4,3

FIGI

FIG. 5 23 55 N o l! 57 \\\\\`\*\*56 :5 I\ 43 INVENTORS. Q I EDWARD H.YONKERS ATTORNEYS RONA EH R BYZ/ Lof gap United States Patent O3,154,718 SECONDARY LIGHTNING ARRESTER WHH ARC SPINNNG MEANS Edward H.Yonkers, Glencoe, and Ronald il. Huber, Evanston, lll., assignors to.loslyn Mfg. and Supply Co.,

Chicago, Ill., a corporation of' illinois Filed Mar. 16, i962, Ser. No.thltlo 15 Claims. (Qi. S15-e) The present invention relates generally toa lightning arrester and is more particularly concerned with a new andimproved protective device generally known as a secondary lightningarrester for use on a secondary or low voltage circuit.

Secondary lightning arresters are used to protect equipment connected tothe low voltage, secondary circuits and power distribution systems whichusually have their primary or high voltage circuit also protected bylightning arresters or similar devices.

The present invention is concerned with the improved protection of thesecondary circuits of this system and, more particularly, with theprotection of low voltage electrical equipment where it is directly orindirectly exposed to lightning voltages. Such secondary voltages incommon use in this country include those in the 125- to i550-volt rangeof phase-to-ground and phase-to-phase voltages, and on four wire,three-phase multigrounded systems up to about 900 volts phase-to-phase.

It has been found that much of the low voltage equipment used on thesecondary systems cannot be adequately protected by secondary arrestersof prior designs for several reasons. Among these reasons are the sizeor bulk of secondary arresters which inhibit their installation in thevery small space generally available in the equipment to be protected;the high cost of manufacture; the excessive gas blast and the directionof this blast into areas of the equipment where it will damage componentelements; the high impulse level which results in inadequate protectionof low voltage equipment; the excessive follow current drawn which mayresult in smoking up of the interior of the equipment and in damage tothe parts thereof; and the fact that many of the prior secondaryarresters are designed for use in multiphase systems whereas theequipments to be protected by the arrester of the present invention areoften used in single phase systems.

As is Well known, the function of a lightning arrester is to provide alow resistance path to ground in order to prevent the occurrence ofexcessive voltages caused by electrical disturbances and, at the sametime, to present a relatively high resistance under normal operatingconditions so that the diversion of power current from the line isinsignificant. An ideal lightning arrester would switch from its lowresistance condition to its high resistance condition as soon as theabnormal surge has been dissipated, thus limiting the ow of power followcurrent to the period actually required to restore the systern to normaloperation. To perform these functions a lightning arrester consists of acharacteristic element connected in series with one or more isolatinggaps which function to keep the major portion of the normal systemvoltage olf on the valve element in the absence of surges. Thecharacteristic element serves to bypass to ground surge currentresulting from abnormal line voltages and to interrupt the flow ofsystem follow current as soon as the abnormal voltage condition has beendissipated. Known valve type arresters employ a nonlinear resistance orvalving material which has a high resistance for voltages of the orderof the system voltage and has a very low resistance for voltages inexcess of the normal system voltage. Frequent surges through the valveelement will tend to deteriorate the element by fusing the Cice valvematerial together. Consequently, in order to prolong the life of thelightning arrester, it is necessary to minimize deterioration of thevalve material. This problem is particularly difficult when thelightning arrester is small in size and very compact since a minimum ofvalve material may be used. Accordingly, it is desirable to obtainmaximum use of the small amount of valve material which may be insertedin a compact size lightning arrester.

Moreover, diiculty has been experienced in the destruction of thelightning arrester by ilashover along the outside wall thereof betweenthe terminals of the arrester at dirlerent electrical potentials. Thisis especially true when the outside of the arrester is exposed todeleterious atmospheric conditions such as oils and the like.Additionally, Whenever a lightning arrester is made smaller and morecompact, the voltage gradient along the outside surface is generallyincreased so that the tendency to flashover is increased.

It is therefore an object of the present invention to provide alightning arrester which avoids all of the aforementioned disadvantagesof prior secondary arresters.

A further object of the present invention is to provide an improvedsecondary lightning arrester which is small in size and very compact.

A further object of the present invention is to provide an improvedsecondary lightning arrester which is economical to manufacture.

A further object of the present invention is to provide an improvedsecondary lightning arrester which is very effective for its small sizeand low cost.

It is a further object of the present invention to provide an improvedlightning arrester obtaining maximum utilization of the valve materialtherein.

A further object of the present invention is to provide a new andimproved lightning arrester of compact size having improved sparkovercharacteristics.

The foregoing and other objects of the invention are realized by theprovision of a secondary lightning arrester or protective device, smallin size, and having an v isolating gap and valve material and whereinthe spark in the isolating gap is controlled by magnetic means toprovide continuous motion to an arc in the gap. Valve materials are wellknown, and the improved valve material disclosed and claimed in thecopending application of Edward H. Yonkers (Case l-49-Cont.), Serial No.157,293, tiled November i6, 1961, and assigned to the same assignee asthe present invention, is particularly suited for use with the presentarrester. Additionally, the lightning arrester according to the presentinvention 'includes an isolating spark gap formed of a first electrodeof inverted cup-shape having its exterior in engagement with the valvematerial and a second electrode concentrically spaced within the firstelectrode to form the spark gap therewith. Magnetic means are providedproducing an axial magnetic eld through the gap. The spark gap and thevalve material are serially connected across an electric path to providefor the discharge of an abnormally high voltage across the path. Ofcourse, it is understood that normally the second electrode is connectedto one line of a single or multiphase electrical system and the valvematerial is connected through the casing of the arrester to ground.

The invention, together with further objects and advantages thereof,Will best be understood by reference to the following detaileddescription taken in connection with the accompanying drawing, in which:

FIG. 1 is la perspective view of an improved lightning arresteraccording to the present invention;

FIG. 2 is a cross-sectional, elevational view of the improved lightningiarrester of FIG. 1; and

FIG. 3 is a cross-sectional, elevational view of a amarre modiedembodiment of a lightning arrester according to thev present invention.

Referring now to the embodiment of FIGS. l and 2, the improved lightningarrester, generally illustrated at 10, includes 'an outer housing orcasing 11 formed of a cylindrical side wall 12 of aluminum or otherelectrically conductive material and closed at one end by an end wall 13formed of a pair of spaced discs 14 of aluminum or other electricallyconductive material and separated by a resilient gasket 15 of neopreneor other suitable material. An electrically conductive shunt 16 ofsuitable material such as copper interconnects the spaced discs 14. Theother end of the casing 11 contains a threaded mounting flange 17 formedintegral with the side Wall 12 and provided with a mating lock nut 18.The electrical components of the lightning arrester ltlare enclosedwithinthe casing 11 and the mounting flange 17 is provided with anaxially extending central aperture 21 through which is positioned anelectrical insulator Z2 of phenolic resin or other suitable material. Aninsulated electrical lead 23 including Ia conductor 23a passes axiallythrough the insulator 22. A cylindrical inner liner 19 of electricallyinsulating material such as of phenolic resin is positioned completelythroughoutV the length of the side Walll 12 to insulate the componentsWithin the lightning arrester 10 Vfrom direct engagement with theconductive side Wall 12. Moreover, a plurality of electrical insulatorsZita and Zlib are provided for maintaining the components of thelightning arrester in proper spaced relation.

To providea characteristic element for control of low voltage dischargethrough the lightning arrester, the lightning arrester 10 contains asuitable valve material 24. The valve material 24 may comprise siliconcarbide par ticles, as more fully set forth in the above-mentioned cotpending Kapplication of Yonkers. The valve material 24 is contained inthe casing 11 and fills the end of the lightning arrester 10 closed bythe end wall 13.

To provide for a 'sparkv discharge under abnormally high voltageconditions, the lightning arrester to is provided with a cup-shaped rstelectrode 2S of bronze or other suitable electrically conductivematerial which cocperateswith a disc-shaped arcing or second electrode26 of bronze or other suitable electrically conductive materialconcentrioally positioned Within .a cylindrical side Wall portion a ofthe first electrode 25, to form an annular spark gap 27 therebetween.The electrode 25 additionally includes a bottom or end wall 25b closingone end thereof and is provided adjacent its other end with an outwardlyextending ring-shaped portion 25e. The electrode 25 is inverted into thevalve material Z4 to form electrical contact therewith and the outersurface of the side Wall portion 25a and the end Wall Z5b is inengagement with the valve material 24 to form conductivepathsitherewith.

The electrode 26 is supported on the inner end of the insulator 22 by aninsulating washer 3i) and is connected to the inner end of theelectrical conductor 23a. A crimped copper rivet 31 secures the innerend of the electrical conductor Y23ato the electrode 25.

In order to provide for control of the motion of an arc Within the sparkgap 27, there Vis provided magnetic means in the form or" a ceramicpermanent magnet 32 concentric'ally positioned around the spark gap- 27and provided with axially extending north and south poles. Ringorwasher-shaped ferrous pole shoes 33 and 34 cooperating With the magnet32 to concentrate the magnetic iield and direct it axailly through thespark gap 27.

From the above-detailed description of the improved lightning arrester,its operation is believed clear; however, briey, it will be appreciatedthat an abnormally high voltage to the lead 23 will provide an arcdischarge across the spark gap 27. As the spark passes through the gap27 at right angles to the magnetic field induced by a magnet 432, theeld causes motor action on the arc current spinning the arc Iaround theannular gap. The arc travels so rapidly around the electrode surfacesthat the electrode surfaces do not reach the mel-ting point. As :aresult, electrode beading is minimized and the arc is cooled landdeionized 'and extinction thereof occurs at the i'irst 60-cycle currentzero. Moreover, the inverted derby hat construction of the electrode 25which contacts the valve material 24 provides -for large surface contactbetween the electrode 25 and the valve material 241 so Ithat therelatively small amount of valve material provided may be fullyutilized. The large contact surface tends to form a multitude ofelectrical channels through the valve material 24 so that the currentwill be distributed into the central area of the valve material 24.Moreover, the comparatively long outer side wall provided by the casing11 minimizes the flashover along the surface of the device. Accordingly,the lightning arrester 1t) which is very eiective for its size and costis provided.

Referring now to the embodiment of FIG. 3, there is illustrated amodified form ci lightning arrester 49 according to the presentinvention. As therein illustrated, the lightning arrester di) includes acasing 42 of aluminum or other electrically conductive material havingone end closed by Ian end wall 42 and further provided with a threadedmounting ange 43 at the other end thereof. rille casing d1 includes acylindrical side wall 44 of aluminum or other suitable electricallyconductive material. Additionally, Ithe casing 41 is provided with acylindrical inner sleve 4S of electrically insulating material such asphenolic resin.

To provide for the extinction-of low voltage flows, the ligtningarrester 40 is provided 'with a valve material 46 iilling the closed endthereof and formed of silicon carbide as more fully described in theabove-mentioned copending application tiled by Yonkers or with othersuitable valve material.

To provide a spark gap 47 to provide a high resistance impedance to thelow voltage line circuit, there is provided a first electrode assembly48 of generally inverted derby hat or cup shape and including acylindrical side portion 43 formed of copper or other suitableelectrically conductive material. The rst electrode ditv includes atirst member 49 having a cylindrical side wall portion 49a closed at oneend by an end Wall 4-9b and provided adjacent itsvother end with anoutwardly extending ring-shaped ilange 49C. Additionally, the firstelectrode 43 includes a ringor torus-shaped electrode member 50electrically connected to the flange 49h. A second electrode S5 isprovided concentrically positioned with the iirst electrode 48 andsupported from an insul The second` lating member 56 within the casingV41. electrode 55 is ofho'llow cylindrical shape forming a disc-shapedmember having a cylindrical side wall 55a closed at one end by an endwall 5517 and open at its other end to receive a stud 57 extendingthrough an axial opening 58 in the insulating member Se. An elect-ricalconductor 59a of an electrical lead 59 extends through the opening 5Sand is electrically secured with the stud S7.

To provide 4for the control of the movement of an are in the spark gap47, magnetic means comprising a ceramic permanent Imagnet 60 ispositioned within `the Ihollow electrode 55 concentric with theelectrodes 48 and 55 and having axially extending poles to provide ageneral axial magnetic ield through the spark gap 47. A pair ofdisc-shaped pole shoes 61 and 62 positioned against opposite ends of themagnet titl concentrate the magnetic field and direct it `axiallythrough the spark gap 47, very effective to utilize the magnet 619,.

From vthe above description, it will be understood that the lightningarrester of the embodiment of FIG. 3 operates in a manner similar tothat heretofore described in `connection with the embodimnet Vof FIGS. land 2; specically, the magnetic means 6i? provides for continuousmovement of an arc in the spark gap 47 and, additionally, the invertedderby-shaped electrode structure 43 is effective tc provide maximumutilization of the valve material 46.

Although various illustrative embodiments of the present invention lhavebeen illustrated and described, it will be apparent yto those skilled inthe art that numerous changes and modifications can be made and it is,therefore, intended by the appended claims to cover all suchmodifications as fall Within the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A lightning arrester comprising a housing, valve material in saidhousing, a rst electrode of inverted cup shape having its exterior inengagement with said Valve material, -a second electrode concentricallyspaced within said first electrode `to form an annular spark gaptherewith, and means connecting said second electrode, first electrode,and valve material in an electrical circuit.

2. A lightning arrester comprising a housing, valve material in saidhousing; a first electrode of inverted cup shape having its exterior inengagement with said valve material; a second electrode concentricallyspaced within said first electrode to form `an annular'spark gaptherewith; means connecting said second electrode, first electrode, andvalve material in an electrical circuit; and means producing an axialmagnetic field through said gap.

3. A Ilightning arrester comprising a housing closed at one end, a firstelectrode of inverted cup shape including .a side wall and an end wallwith the end wall positioned toward the closed end of said housing, asecond electrode spaced withinfsaid first electrode to form a spa-rk gaptherewith, grandular valve material filling the space in said housingbetween said first electrode and `the closed end of said housing, andmeans for connecting said first electrode, said second electrode, andsaid valve material in an electrical circuit.

4. A lightning arrester comprising a cylindrical housing closed at oneend, valve material lling the closed end of said housing, a firstelectrode of inverted hat shape having its exterior in engagement withsaid valve material, a disc-shaped second electrode concentricallyspaced within said first electrode to form an annular spark gaptherewith, means connecting said first elec trode, spark gap, secondelectrode, and valve material serially in an electrical circuit, andmeans producing an axial magnetic field through said gap.

5. A lightning arrester as set forth in claim 4 above wherein saidsecond electrode is hollow and wherein the lastnnentioned means includesa plug-shaped permanent magnet positioned in said second electrode.

6. A lightning arrester as set forth in claim 4 above wherein thelast-mentioned means comprises a ringshaped permanent magnet havingpoles extending axially and concentrically positioned around said firstelectrode.

7. A lightning arrester as set forth in claim 6 above wherein thelast-mentioned means includes a pair of ringshaped pole memberspositioned at opposite ends of said magnet.

8. A lightning arrester comprising a conducting 'casing including acylindrical side wall closed -at one end by an electrically conductiveelement; an insulating sleeve within said casing; grandular arrestervalve material in said one end of said casing; an open invertedcup-shaped first electrode in said housing including a cylindrical sidewall portion closed at one end by .a bottom wall and provided with anoutwardly extending ring-shaped portion lat the other end, at least aportion of said side wall and bottom wall of said electrode extendinginto and in electrical engagement with said valve material; adisc-shaped second electrode extending at least partially within andconcentrically with said first electrode and closely spaced from saidportions thereof forming an annular spark gap with at least one of saidportions, means for completing an electrical circuit through said sparkgap between said electrodes and including said casing and said valvematerial serially positioned with respect to said first electrode, andmagnetic means concentrically positioned with and axially aligned withsaid annular gap for inducing continuous arcuate motion to any arc insaid gap.

9. A lightning arrester as set forth in claim 8 above wherein thelast-mentioned means comprises a ringshaped permanent magnet havingpoles extending axially and concentrically positioned around said firstelectrode.

10. A lightning arrester as set forth in claim 9 above wherein thelast-mentioned means includes a pair of ringshaped pole memberspositioned at opposite ends of said magnet.

l1. A spark gap unit for use in a lightning arrester of the typeincluding a housing closed at one end and having valve material fillingthe space in the housing adjacent the closed end; said spark gap unitcomprising a first electrode of inverted cup shape including a side walland an end wall adapted to be positioned in a housing with the end wallpositioned toward the closed end of the housing against said valvematerial, a second electrode spaced within said iirst electrode to forma spark gap therewith, and means for connecting said first and secondelectrodes in an electrical circuit.

12. A spark gap unit for use in a lightning arrester of the typeincluding a housing closed at one end and having valve material fillingthe space in the housing adjacent the closed end; said spark gap unitcomprising a first electrode of inverted hat shape adapted to have itsexterior in engagament with the valve material, a discshaped secondelectrode concentrically spaced within said first electrode to` form anannular spark gap therewith, means .connecting said iirst electrode,spark gap and second electrode serially in an electrical circuit, andmeans producing an axial magnetic field through said gap.

13. A lightning arrester as set forth in claim l2 above wherein saidsecond electrode is hollow and wherein the last-mentioned means includesa plug-shaped permanent magnet positioned .in said second electrode.

14. A lightning arrester as set forth in claim 12 above wherein thelast-mentioned means comprises a ringshaped permanent magnet havingpoles extending axially and concentrically positioned around said firstelectrode.

15. A lightning arrester as set forth in claim 14 above wherein thelast-mentioned means includes a pair of ringshaped pole memberspositioned at opposite ends of said magnet.

References Cited in the file of this patent UNITED STATES PATENTS

2. A LIGHTNING ARRESTER COMPRISING A HOUSING, VALVE MATERIAL IN SAIDHOUSING; A FIRST ELECTRODE OF INVERTED CUP SHAPE HAVING ITS EXTERIOR INENGAGEMENT WITH SAID VALVE MATERIAL; A SECOND ELECTRODE CONCENTRICALLYSPACED WITHIN SAID FIRST ELECTRODE TO FORM AN ANNULAR SPARK GAPTHEREWITH; MEANS CONNECTING SAID SECOND ELECTRODE, FIRST ELECTRODE, ANDVALVE MATERIAL IN AN ELECTRICAL CIRCUIT; AND MEANS PRODUCING AN AXIALMAGNETIC FIELD THROUGH SAID GAP.